Interventions in the vascular bed have been increasing dramatically within the past few years. Not only are coronary interventions done with sophisticated tools, higher success rates and new indications, but also interventions in other vessels are performed with increasing success and broadening indications.
Time, speed, cost, precision, accuracy, and final outcome are the major determinants of any progress in the catheterization laboratory. While it has been customary for many years to introduce a guide wire into the lumen and to advance over that guide wire an instrument such as a balloon catheter to work at the specific site, then exchange this balloon catheter for a second one, and finally for therapeutic instruments such as stent delivery catheter, the complexity of such a procedure prohibits very short procedural time for the operation or intervention. In addition, increased amounts of contrast dye are required to localize each of the individual instruments. The use of contrast dye has negative effects on the renal function, on the myocardial function, and on the cerebral function in those patient treated in a catheterization laboratory.
Clearly, it is beneficial for both parties, the medical team and the patient, to reduce the interventional time and systems needed to a minimum.
Clinical evidence has shown that excellent long term results can be obtained with primary stenting. It is understood that with primary stenting no pre-dilatation of a coronary stenosis occurs, since the delivery system which includes a balloon mounted stent is suitable to pass through even a tight lesion.
A problem encountered with stenting is associated with the embolization of debris resulting from the target lesion site which undergoes a considerable change in physical characteristics. The arteriosclerotic masses which cause stenosis in the vessel, such as a coronary, renal, peripheral or carotid stenosis, can be somewhat manipulated when means such as stenting are applied to increasing vessel lumen size. For example, a stenosis which only has a diameter of 0.3 mm is dilated to a diameter of 3.5 mm. Part of this stenosis is squeezed into the vessel wall, but part of this arteriosclerotic build-up, consisting of cholesterol crystals, fibrous tissue, collagen matrix, degenerated inflammatory cells and even most extreme calcifications, are not only displaced into the wall but are also partly embolized to a distal site. At the distal site the emboli cause a perfusion defect, which is in the case of a cardiac intervention a myocardial ischemia and myocardial necrosis, finally resulting in small areas of infarcted myocardium. In case of a carotid operation it is a cerebral perfusion defect which might be transitory, which also might result in a major stroke by blocking important cerebral perfusion downstream following an intervention.
Normally a tight fibrous cap protects the vessel from embolization of this material. With the application of pressure by a balloon, the fibrous cap ruptures, and part of the debris embolizes to a distal site, according to where the blood flows. In the case of the coronary anatomy this is toward the downstream of the myocardium. In the case of a renal artery, this is the renal parenchyma, and in the case of a peripheral artery, this is the peripheral muscles. While embolization in the peripheral muscles can be more easily compensated for at a local site, an embolization, from a carotid artery in the brain for example, has major consequences for the patient, including stroke and disability. Newer methods, such as the utilization of a stent in the affected area, are not really helpful to prevent this type of embolization.
It is a primary aim of the present invention to provide an improved interventional device which enables rapid and effective treatment of a stenosis in a body vessel, and confines the distal embolization of debris from an intervention to a collection area where it is readily removable from the patient""s body.
Another aim of the invention to provide an automatic sequential deployment of debris collection means and stenting means so that by the time the stent is deployed, a debris trap has sprung to assure that little or no debris will be allowed to embolize downstream of the intervention.
Yet another aim is to provide a method for operating a balloon catheter stent delivery system in such a way that a debris collection device is automatically deployed immediately prior to deployment of the stent to prevent an escape of debris that would otherwise embolize downstream of the delivery system during an intervention.
The present invention aims to improve both the challenge of an easier application of an interventional device at the target lesion site with a higher primary success rate despite a tight stenosis, and to effect deployment of a shielding device that protects the downstream perfusion from embolization, and to operatively combine these two devices in order to make an intervention faster, more precise, with fewer side effects and lower cost.
According to the invention, an interventional device for alleviating a stenosed condition in a body lumen includes a catheter; a fixed guide wire located distally on and integral with the catheter; a stent delivery system with a stent located proximally of the fixed guide wire; and a device mounted on the guide wire for collecting debris dislodged by the stent during alleviation of the stenosed condition. The debris collecting device is arranged and adapted to be deployed automatically in advance of deployment of the stent during the same operation of the interventional device that results in deployment of the stent. The debris collecting device includes a porous material mounted in a collapsible mechanism on the fixed guide wire, a first balloon for opening the collapsible mechanism upon inflation and for closing the collapsible mechanism upon deflation. The stent delivery system includes a second balloon on which the stent is mounted for deployment upon inflation and for removal from the delivery system upon deflation. A common pressurization system is provided for inflating and deflating the first and second balloons. The first and second balloons are selected to have different pressurization-diameter characteristics to enable the automatic deployment of the debris collecting device in advance of deployment of the stent.